Power Equipment Starting System

This invention relates to a starting interlock system for power equipment in general, and more particularly a starting interlock system for electric-powered lawn mowers.

It is desirable to have a starting system for power equipment that requires a deliberate attempt on the part of the equipment user to start the equipment.

It is desirable to lessen the probability of unauthorized starting of the equipment and additionally to provide a system which ceases to operate when the operator leaves the control handle. Inadvertent starting of the equipment should be difficult, particularly as the operator performs repair or maintenance functions on the equipment. It is also advantageous to have a system requiring positive operator effort to keep the power equipment running.

Prior art devices are known which do require not only a deliberate attempt to start power equipment, but also a concentrated effort to maintain the equipment running. Such devices may include an ignition switch operated by a key in conjunction with a dead man handle that must be continually manually depressed to maintain the equipment running. (One of such devices is shown in U.S. patent application Ser. No. 601,345, filed Aug. 4, 1975.) In the system disclosed in that application, a key operated ignition switch is mounted on a lawn mower handle in close proximity to the operator's hand grip. A squeeze handle must be continually depressed by the operator and upon release causes the equipment to turn off. Electrical wires lead from the switch housing on the handle to the motor mounted on the mower frame.

Problems arose in the use of prior art devices, particularly those having live electrical wires leading from the equipment handle to the equipment main frame. Shorts in these electrical wires could lead to equipment malfunctions. Additionally, the prior art devices included a relatively large number of parts both increasing the chances of malfunction and raising the cost of the device.

The present invention solves the problems of the prior art devices by providing a simple, low cost, easy to assemble starting interlock requiring the manipulation of a key lock and a dead man handle to permit energization. The electrical switch associated with the equipment motor is mounted on the frame housing and actuated by a bowden wire cable connected to a manual interlock device.

The present invention is a starting interlock system for power equipment and includes a cam pivotally mounted to the operator's handle for rotation between first and second cam positions and having first and second cam surfaces and apparatus responsive to the cam position for energizing the equipment when the cam is in the first cam position. The invention further includes a lever pivotally mounted to the operator handle for rotation between energization and release positions and having a first contact surface that in the energization position engages the first cam surface in the first cam position preventing the cam from rotating to the second cam position and a second contact surface that, in the release position, engages the second cam surface in the second cam position to lock the cam in the second cam position, and means biasing the cam toward the second cam position. Since the lever and the contact surfaces associated therewith merely maintain the cam in an already established position, the invention also includes means for permitting pivoting the cam against the biasing means to the first cam position, which may be an insertable key in some embodiments.

The lever must be continuously manually held in the energization position by the operator. The first cam surface is disposed relative to the pivot points of the cam and lever such that upon release of the lever, the contact and cam surfaces disengage allowing the lever to rotate to the release position under the influence of gravitation pull while the cam rotates to the second cam position.

In one specific embodiment of the present invention, the cam is mounted in a housing having an opening through which a removable key is inserted to rotate the cam from the second to the first cam position. The opening in the housing has an enlarged portion and an elongated slot extending therefrom. An annular disc disposed about a cylindrical projection on the key has a diameter smaller than the enlarged portion of the opening but larger than the width of the elongated slot. Thus the key, upon rotation of the cam to the first cam position, is retained by the elongated slot and cannot be removed.

Finally, in one embodiment, the apparatus responsive to cam position to energize the equipment is an electrical switch connected to the cam by a bowden wire cable. The switch is spring biased toward a de-energized position corresponding to the second cam position. Upon rotation of the cam to the first cam position, the bowden wire exerts a force on the switch overcoming the biasing spring and turning the switch to the energization position.

The operation and advantages of the invention will be appreciated with reference to the drawings, detailed description of the preferred embodiment, and the claims.

FIG. 1 is a fragmentary view in perspective of a power equipment handle incorporating the actuating mechanism for my new starting interlock system;

FIG. 2 is an elevational view of the actuating mechanism shown in FIG. 1, portions thereof being broken away to show the details of construction with the system components in a position which corresponds to a braking or deenergization mode of the equipment;

FIG. 3 is a view similar to that shown in FIG. 2 with the system components in a mode corresponding to an energization mode of the equipment;

FIG. 4 is a view in perspective of an electrical switch operated by the actuating mechanism; and

FIG. 5 is a view in exploded perspective of a portion of the actuating mechanism.

The following description will relate to an embodiment of the invention as it is applied to a lawn mower. Referring to the drawings, wherein like numerals represent like parts throughout the several views, there is shown in FIG. 1 designated generally as 10 an upper portion of a handle which is attached at its lower end to the frame of the lawn mower. The upper portion 10 is generally U-shaped having legs 12 and 14 and a connecting hand grip 16. Secured to leg 14 is an interlock device housing 18. Pivotally mounted within housing 18 and to opposite leg 12 is an implement dead man lever 20. The interlock device functions so that the equipment will run only while the dead man lever 20 is raised against the hand grip 16 as illustrated more specifically in FIG. 3. Additionally, the implement will run only upon rotation of a cam 26 into an energization position. This is permitted by insertion of a key 22 into an opening 24 in the housing 18 into contact with cam 26, and manual rotation of the cam by the key to energize the equipment. The specific operation of the key 22 and lever 20 interlock will be described more specifically with respect to FIGS. 2 and 3.

FIG. 2 illustrates the relation of the interlock device elements in the implement braking or deenergization mode. The device includes a cam 26 pivotally mounted within the housing on a shaft 28. Attached to the cam is a bowden wire control cable 30 which extends through a plastic tubing 32 along handle 10 to the mower frame. As shown in FIG. 4, the opposite end of the cable is attached, through a spring 33 which takes up cam overtravel, to an actuating member 34 of an electrical switch designated generally as 36. The switch may be a two-way switch having an energization and a braking or de-energization mode. Switch 36 is secured to the mower frame. A spring 38 biases switch 36 to a normally de-energization position. Rotation of cam 26 in a clockwise direction to the position shown in FIG. 3 exerts a force on cable 30, causing member 34 to move, against the bias of spring 38, to an energization position.

Dead man lever 20 is pivotally mounted to leg 14 of the U-shaped handle 10 and the housing 18 about a shaft member 40. Pivotally mounted to shaft 40 is an arm 46 having a first contact surface 48 which engages a first cam surface 50. The lever 20 has a projecting arm portion 42 with a second contact surface 43 that engages cam 26 at a second cam surface 44. Spring 52 is connected between the arms 42 and 46 and tensioned to urge the arms together. The arm 46 has a stop portion 54 which cooperates with a stop engaging member 56 on the handle 20 to maintain the arms a predetermined distance apart.

With particular reference to FIG. 5, the structure of the key 22 is more specifically illustrated. The key has a grasping portion 58 and a cylindrical projection 60 for insertion in an aperture 62 in cam 26. Integral with the cylindridal projection 60 is a first annular disc 64 having a diameter somewhat smaller than the largest portion 66 of the opening 24 in the housing 18. This sizing permits first annular disc 64 and portions of projection 60 which function as the working portion of the key to be positioned within the housing when the key 22 engages aperture 62 in cam 26. Extending from the opening 66 is an elongated slot 68 whose width dimension is smaller than the diameter of the annular disc 64. A second annular disc 65 is integral with the grasping portion 58 and has a diameter larger than the widest dimension of the elongated slot 68 and, as shown in FIG. 3, remains outside the housing when key 22 engages aperture 62 in cam 26. When the cam is rotated to the energization or first cam position by the key disc 64 is captivated by the housing, since its diameter is larger than the width of the elongated slot along which projection 60 rides. Thus, the key cannot be removed from the housing. A tab 61 contacts cam 26 in the second cam position to retain the cam in position against the spring biasing force of spring 38 in switch 36.

The operation of the device will now be described particularly with reference to FIGS. 2 and 3. FIG. 2 illustrates the relative positions of the device elements in the braking or de-energization mode. In this configuration, the surface 43 contacts the cam surface 44 on the cam 26 if an attempt to rotate cam 26 to an energization position is made. The force established between contact surface 43 and cam surface 44 has a component directed counterclockwise in a plane normal to the axes of shafts 40 and 28. Therefore, cam 26 cannot be manually rotated to the first cam position until level 20 is rotated to the energization position disengaging contact surface 43 from cam surface 44.

To energize the lawn mower, key 22 is inserted within the enlarged opening 66 and into the aperture 62 in the cam 26. Lever 20 is grasped by the operator and pulled toward the hand grip 16. As dead man lever 20 pivots toward hand grip 16, and arm 42 becomes disengaged from cam surface 44, arm 46 rotates clockwise into contact with top surface 51 of the cam. The operator then rotates cam 26 clockwise by moving the key along elongated slot 68. Arm 46 will ride on surface 51 until cam 26 is rotated sufficiently so that contact surface 48 of arm 46 drops into contact with cam surface 50. In the energization mode position illustrated in FIG. 3, arm 46 applies a retaining force to the cam preventing its counterclockwise rotation. Upon release of the lever 20, the lever will rotate counterclockwise due primarily to gravitational forces. The lever 46 will in response rotate upward, disengaging from surface 50 allowing cam 26 to return to the de-energized position shown in FIG. 2 under the biasing force of spring 38, transmitted by bowden wire cable 30 to cam 26. Spring 38 will return the electrical switch to the braking position.

The position of shafts 28 and 40 about which cam 26 and lever 20 rotate with respect to each other and to the orientation of the cam surface 50 is critical to the operation of the interlock device upon release of lever 20. More particularly, as shown in FIG. 3, cam surface 50 is disposed in a plane normal to the axes of shafts 28 and 40. In the energization position of the lever 20 the force exerted by cam surface 50 upon end surface 48 of the arm 46 transmitted by biasing spring 38 to the cam 26 has a component directed so that it acts upon contact surface 48 to impart pivotal movement to lever 20 in a counterclockwise direction. Thus upon release of lever 20, this outward force swings arm 46 counterclockwise out of engagement with cam 26 while lever 20 rotates downward under the influence of the gravitational pull. Thus it will be appreciated that the implement will operate only after pivotal movement of lever 20 against the hand grip 16, insertion of the key 22, and clockwise rotation of cam 26. Therefore, if the implement operator releases the lever, the implement will, in response, shift to a de-energize mode. Additionally, since the equipment cannot be started without the key 22, the possibility of unauthorized starting of the equipment is minimized.

As previously mentioned, spring 52 is tensioned to urge the arm 46 toward the arm 42. In the braking or de-energization mode shown in FIG. 2, stop 54 contacts stop engaging member 56 on handle 20 to maintain a predetermined distance between arms 42 and 46 to permit limited travel of the arm 46 before it comes into contact with the top surface 51 of the cam 26. Spring 52 facilitates ease of operation of lever 20 in that the operator may initially rotate the lever toward the energization position followed by rotation of the cam. Were the spring not included, the operations would necessarily have to be made substantially simultaneously.

Thus, it will be appreciated that the starting interlock disclosed is a mechanism which permits the starting and running of a mower or other equipment only upon deliberate control by the operator.